Cruise control is a speed control system that maintains
a desired vehicle speed under normal driving conditions. However, steep grades
may cause variations in the selected speeds. The electronic cruise control
system has the capability to CRUISE, COAST, RESUME SPEED, ACCELERATE,
and TAP-UP or TAP-DOWN.
The main parts of the cruise control system are:
• | The cruise control module assembly |
• | The function control switches |
• | The cruise control release switch |
• | The stoplamp switch assembly |
• | The vehicle speed sensor |
The cruise control system uses the cruise control module assembly to
maintain the desired vehicle cruise speed and operation. The cruise control
module assembly has a controller and an electric stepper motor to vary the
throttle in each different cruise control mode. Two components in the module
assembly help to do this. The electronic controller and the electric stepper
motor. The controller monitors vehicle speed and operates the stepper motor.
The stepper motor operates in response to the controller, to maintain the
desired cruise speed. The stepper motor moves a strap that is attached to
the cruise control cable which moves the throttle linkage. The cruise control
module assembly contains a low speed limit which will prevent system engagement
below a minimum speed of 40 km/h (25 mph). The module assembly is
not serviceable.
The operation of the controller is controlled by the function control
switches located on the steering wheel. The cruise control functional
control switches include the ON/OFF, SET/COAST, R/A (resume/accelerate).
The switch assemblies provide driver control of the cruise control system.
The cruise control release switch and stoplamp switch are used to disengage
the cruise control. A release switch assembly and a stoplamp switch assembly
are mounted on the brake pedal bracket . To disengage the system the driver
presses the brake pedal. The speed of the vehicle at brake actuation will
be stored in the memory of the cruise module.
With cruise control, you can maintain a speed of about 40 km/h (25 mph)
or more without keeping your foot on the accelerator. When the driver turns
off the on/off switch or ignition switch, the cruise control turns off. The
vehicle speed stored in the memory of the cruise module will be lost.
Ignition 1 voltage is supplied from the cruise control
fuse, to the cruise control module. The cruise control module is grounded
to the chassis. When the cruise control ON/OFF switch is on, ignition 1 voltage
is applied to the cruise control on switch signal circuit of the cruise control
module. If the driver has not pressed the brake pedal, ignition positive
voltage is supplied through the TCC Brake switch, to the cruise control
TCC Brake switch signal circuit of the cruise control module. When the driver
presses the brake pedal, battery positive voltage is supplied from the stoplamp
fuse, through the closed stoplamp switch to the stoplamp switch signal circuit
of the cruise control module. When the SET/COAST button is pressed , ignition
positive voltage is applied to the set/coast switch signal circuit of the
cruise control module. When pressing the R/A (resume/accelerate), ignition
positive voltage is applied to the resume/ accelerate switch signal circuit
of the cruise control module.
The cruise control module receives a vehicle speed signal input from
the Powertrain Control Module (PCM). In operation, the voltage varies between
0 V and 5 V.
The cruise control module, cruise engaged signal circuit, sends a signal
to the PCM when cruise is engaged. The PCM will then send a message to the
instrument panel cluster (IPC) to turn on the cruise light. The cruise control
module, cruise cancel signal circuit, is a circuit used by the PCM to inhibit
cruise control when conditions inconsistent with cruise operation are present.
The PCM will inhibit cruise control:
• | When vehicle speed is less than 40 km/h (25 mph). |
• | When PARK, REVERSE, NEUTRAL, or 1st gear is indicated. |
• | With high engine RPM (fuel cut-off) |
• | When vehicle speed is to high |
• | When an over or under charged battery voltage condition exists |
• | Antilock brake system/traction control system is active for more
than 2 seconds |
• | A 6 MPH or more decrease in non-drive wheel speed in 0.4 seconds
with out seeing the extended brake travel contacts of the TCC/Brake switch
transition. |
If the PCM determines that any of the cruise control inhibit conditions
are present, the PCM will disengage the cruise control . The PCM accomplishes
this by opening the cruise control inhibit signal circuit. If the cruise
engaged signal, sent by the cruise control module to the PCM, indicates that
the cruise control is still engaged after the PCM has requested that the
cruise control disengage, the PCM sets a DTC.